The invention relates generally to power-driven conveyor belts and, more particularly, to means and methods for operating modular conveyor belts interconnected row to row by hinge pins even when hinge pins migrate from their operative positions.
Conventional modular conveyor belts and chains are constructed of modular links, or belt modules, arranged end to end and side to side in belt rows. Spaced-apart hinge eyes extending from each end of the modules include aligned openings. The hinge eyes along one end of a row of modules are interleaved with the hinge eyes of an adjacent row. Pivot rods, or hinge pins, journalled in the aligned openings of interleaved hinge eyes, connect adjacent rows together end to end to form an endless conveyor belt capable of articulating about a drive sprocket or drum at the hinge formed between adjacent belt rows.
Because they do not corrode and are easy to clean, modular plastic conveyor belts are often used instead of metal belts, especially in food-related applications. Usually, the hinge pins in plastic belts are also made of plastic. Hinge pins are retained in the hinges by various means. Sometimes the hinge pins terminate at both ends in enlarged heads that are too big to enter the openings in the hinge eyes. In other pin retention schemes, integral belt structure in the vicinity of the hinge eyes obstructs the pin from exiting the aligned openings. Still other pin retention schemes use insertable occluding pieces to keep the pins in place. But all of these rod retention schemes can fail. Extreme or rapidly changing temperatures, for example, can cause pin retention problems because of stresses applied to the pins by uneven expansion and contraction of the pin, the interconnected belt modules, and the retention elements. These stresses can cause, for example, the heads to pop off, the retention structure to give way, or the insertable occlusions to move out of retaining positions. Once pin retention is lost, a hinge pin can work its way completely or part way out of the belt. As an unretained hinge pin migrates toward one side of the belt, the edge module from which the hinge pin migrates is no longer connected to its neighbor along that end of the row. This problem is especially acute in modules with narrower edge modules. If the edge module is not supported from below or along its outer side edge, it will pivot about its other hinge pin out of alignment with the other modules in the row. Once out of alignment, the edge module is more susceptible to catching on conveyor structure and to improperly engaging drive and idler sprockets. Damage to the belt can occur quickly.
During the repair or installation of a modular conveyor belt, a hinge pin has to be inserted into the interleaved hinge eyes of adjacent rows to connect the rows together. It is often difficult to align the modules on each row because each module of the row is free to rotate about the hinge pin at the other end of the row. Each module of the row can rotate independently of the others. The more modules there are per row, the harder it is to line them all up. And then the modules on the adjacent row have to be lined up, too. Aligning the modules along adjacent rows of a wide belt before interleaving the hinge eyes to ready the belt for insertion of the hinge pins can be a time-consuming and frustrating task.
Thus, there is a need to improve modular conveyor belts to prevent or delay the damage that can be caused by a migrating hinge pin. There is also a need for a modular conveyor belt whose hinge eyes can be readily aligned for easy insertion of a hinge pin.
These needs and others are satisfied by a modular conveyor belt having features of the invention. The belt is of the type constructed of a series of rows of belt modules arranged side by side. The modules extend in the direction of belt travel from a first end to a second end and through their thickness from a generally planar top surface to a generally parallel bottom surface. A first set of hinge eyes is arranged along the first end; a second set of hinge eyes is arranged along the second end. The first set of hinge eyes of a row is interleaved with the second set of hinge eyes of an adjacent row. A hinge pin extends through the interleaved hinge eyes to interconnect the modules along the adjacent rows at a hinge. Mating engagement structure on confronting side-by-side belt modules in a row maintains the side-by-side modules in alignment even in the absence of a hinge pin extending through any of the hinge eyes of at least one of the modules along one of the ends of the row. The mating engagement structure includes a protrusion extending from a first side of a first belt module and a receptacle formed at the confronting second side of a second module in the row. The receptacle is defined by discontinuous wall structure with a gap opening toward the top or bottom surface of the modules, or toward both surfaces. The receptacle receives the protrusion from the adjacent module through the gap in the discontinuous wall structure as the side-by-side modules are engaged from a direction perpendicular to the generally planar top and bottom surfaces. Once engaged, the modules remain aligned even in the absence of a connecting hinge pin.
The protrusion is, in one version, a generally rectangular pad; and the receptacle is a recess defined by a pair of generally vertical walls formed in the second side of the second belt module. This engagement structure is especially useful when one of the engaged modules is an edge module forming a side edge of the belt. In another version, the receptacle is U-shaped, with the wall structure defining the bottom of the U forming a stop for the protrusion. In yet other versions, the protrusion is T-shaped or a pair of parallel ribs.
A method for maintaining side-by-side belt modules aligned in a belt row in the absence of a hinge pin along at least a portion of an end of the belt row includes: forming a protrusion on a first side of a first belt module; forming a receptacle defined by discontinuous wall structure forming a gap in the receptacle on a second side of a second belt module; engaging the protrusion with the receptacle through the gap in the discontinuous wall structure of the receptacle; and connecting the belt row to an adjacent belt row with a hinge pin. The protrusion and receptacle, in various versions of the invention, can be formed by injection-molding, machining, or affixing.
Thus, an improvement to the construction of a conveyor belt and a method for constructing such a belt result in a belt that is easier to install or repair and that can be operated even after a hinge pin has migrated from its usual position.